Apparatus for forming and removing condensed metal crowns



Dec. 27, 1966 D. M. PEPLINSKI APPARATUS FOR FORMING AND REMOVING CONDENSED METAL GROWNS Filed April 9, 1964 United States Patent 7 Claims. (cl. 266-19) This invention relates to apparatus for condensing metal into crowns and removing the crowns from the condenser.

Alkaline earth metals and particularly Mg and Ca can be produced by high temperature reduction under vacuum of metal oxides with Si or similar suitable reducing agents in a retort. The metal is vaporized in the retort and carries over into a condenser where it condenses in the form of a crown. The metal crown is then removed from the condenser. Heretofore it has been the practice to condense the crown in a condenser sleeve which is removable from the condenser for pressing out of the crown. It is desirable to condense at a temperature as hot as possible, i.e. just cooler than the metal melting point, in order to form small crystals and achieve a dense crown. However if the temperature exceeds the melting point the -metal liquifies and is essentially lost. This occurrence is called a hot crown in the trade. Thus temperature regulation in the condensing zone is very important in obtaining a good product and a good yield.

In the known apparatus removable condenser sleeves are used to collect the crown because of the problems of condensate removal from the condenser itself which must be fastened to the retort so as to maintain the high vacuum. But especially because of the vacuum it is difficult to closely control the temperature of the condensation zone in the sleeve since the direct path of heat conduction from the crown to the cooling fluid around the condenser is interrupted over a major portion of the surface of the crown, by a space in which there is a high vacuum.

The object of the present invention is to provide inexpensive reusable apparatus for condensing metal crowns with which condensation temperature can be closely controlled to avoid losses from hot crowns and to achieve the desired crown density.

A further object is to provide apparatus by which crowns can readily and effectively be removed from the condenser as two half cylinders or, more accurately, two tapered segments of a tapered cylinder which can be conveniently stacked and shipped.

Broadly the invention comprises apparatus for the high temperature vacuum reduction and condensation of metal into metal crowns which comprises a retort having a closed hot end and an open cool end, a tubular condenser having a hot end and a cool end, its hot end being sealed vacuum tight to the cool end of said retort, said condenser being tapered over a major portion of its length, inwardly toward its hot end at an angle of from 0.5 to and a wedge in said condenser disposed along the axis thereof, having side walls tapering inwardly toward said hot end at an angle of from 0.5 to 10 and having a top wall and a bottom wall in loose fitting relation to the tapered portion of said condenser.

The invention is described with reference to the accompanying drawing in which:

FIGURE 1 is a plan view of the wedge in place in which the retort-condenser unit is shown in section along the centre line thereof, and

FIGURES 2, 3 and 4 are a plan, an elevation and an end view, respectively, of the wedge.

In FIGURE 1 a retort 1 is mounted centrally in furnace wall 2. The retort is commonly made of thick walled alloy steel and has a closed hot end 3 and an open cool end 4. Tubular condenser 5 is sealed vacuum tight adjacent its hot end 6 to the cool end 4 of the retort as by butt weld 8. The condenser is commonly made of thinner walled alloy steel and has on its cool end 7 a removable lid 9 which can be sealed vacuum tight as by rubber gasket 10. A water jacket 11 surrounds condenser 5 and vacuum may be drawn on the system through conduit 12.

Condenser 5 is tapered inwardly toward its hot end 6 over at least a major portion of its length at an angle of from 0.5 to 10.

Metal crown supporting member or wedge 13 stands upright in the condenser 5 disposed along the axis thereof and has a pair of side walls 14. which are the major surfaces of the member, a top wall 15, a bottom wall 16, which are the minor surfaces thereof, a large cool end 17 and a small hot end 18. The top and bottom walls 15 and 16 are tapered correspondingly to the sleeve and are in loose fitting engagement therewith. The side walls 14 taper inwardly toward the hot end 18 at an angle of from 0.5 to 10. The wedge may be provided with transversely extending bafile plate 19 at its cool end 17. Plate 19 has an aperture 20 therein for receiving a hooked tool used to dislodge and pull the wedge and crown out of the condenser. Circumferential lugs 21 may also be provided on the plate 19 to assist in dislodging the crown from the condenser. m

In operation a charge 22 consisting of a metal oxide and a reducing agent is placed in the retort and then the wedge is inserted and pushed inwardly toward the hot end of the condenser until the baffle 19 and the top and bottom walls 15 and 16 come into loose fitting engagement with the condenser. A clearance of up to about is suitable. Lid 9 is then sealed in place, the vacuum drawn and the furnace temperature raised. The metal oxide is reduced to metal which vaporizes. The bafiie plate 19 acts as a heat shield and the water jacket is used to control the temperature 0n the hot side of the bafiie plate in the condensation zone. In practice the condensation zone may extend into the end of the retort. The metal vapour condenses into a crown 23 in the condensation zone in two circular segment sections 24 on either side of the wedge 13. The wedge should be long enough to receive the whole crown and protrude slightly beyond it.

The vacuum is then relieved, the lid 9 removed. A hook may be inserted into aperature 20 in plate 19 to pull with wedge and crown out of the condenser. It may be necessary to knock the crown loose or pry it from plate 19 and lugs 21 may be included to facilitate this. The withdrawn crown may be readily knocked into two halves and separated from the wedge which may be reused.

High vapour pressure impurities from the charge will tend to pass the loose fitting baffle plate and condense toward the cool end 7 of condenser and may be collected and removed by known means. It is desirable to provide a substantial length of condenser on the cool side of the bathe plate 19.

The wedge 13 is preferably constructed of mild steel plate A to /2" thick welded together. However, it could be made in other ways such as by casting to shape with reinforcing ribs in the wedge and plate. The narrow end 18 may conveniently have a width as narrow as /2" and the large end 17 may be about 3 /2" wide. The tapered surfaces should be tapered at, at least a 05 angle so that separation can be achieved by small axial movement despite irregularities in the crown surface. A taper of more than 10 would require unduly large equipment without increased benefit. The preferred taper is about 3. For use with a 10" average diameter condenser the wedge length may suitably vary from about 10" to about 20" with a preferred length of about 14".

In the preparation of Mg crowns, Na and K impurities should not condense significantly in the condensation zone and in the prepartion of Ca crowns, Mg likewise should in major proportion pass the baffle plate to condense on the cool side thereof thereby achieving a purer crown. For this purpose about A" clearance between the baffle plate edge and the condenser is generally suitable or a clearance of in the order of 1% of the cross sectional area. A greater clearance can readily be achieved for a particularly impure charge, by moving the wedge somewhat toward the cool end or by making the bafile plate smaller in diameter than the depth of the wedge at its cool end.

It will be appreciated that the temperature in the condensation zone may be closely controlled because heat has an all metal path to the cooling medium. Accordingly the desired crown density can be achieved and hot crown loss can be avoided.

What is claimed is:

1. Apparatus for the high temperature vacuum reduction and condensation of metal which comprises a retort, a tubular condenser having one end communicating with said retort, said condenser having an interior wall surface of gradually decreasing diameter towards said one end, and a metal crown supporting device comprising a wedgeshaped member having a pair of opposed converging major surfaces and a pair of opposed converging minor surfaces in loose fitting engagement with said wall surface, said member having a longitudinal axis about Which said surfaces are substantially symmetrically disposed, said axis being substantially coincident with the axis of said condenser wall surface, said surfaces of said member all converging towards one end thereof adjacent said one end of said condenser, and a transversely extending baffie plate mounted on the other end of said member and having its peripheral edge in loose fitting relation to the wall of said condenser.

2. Apparatus as defined in claim 1 in which said baflle plate has a centrally disposed aperture therethrough and at least one lug peripherally disposed on the face thereof confronting said retort.

3. Apparatus as defined in claim 1 wherein said baffie plate is circular and at least a portion of the periphery thereof is spaced about inch from said wall surface of said condenser.

4. Apparatus as defined in claim 1 wherein the taper of each of said condenser and wedge-shaped member surfaces is of an angle of about 3 5. Apparatus for the high temperature vacuum reduction of alkaline earth metal oxides and condensation of alkaline earth metals into crowns comprising a retort having a closed hot end and an open cool end, a tubular condenser having a hot end and a cool end, its hot end being sealed vacuum tight to said retort adjacent the cool end thereof, said condenser having its interior surface tapered over a major portion of its length inwardly toward its hot end at an angle of from 0.5 to 10 and a wedge in said condenser disposed along the axis thereof having side walls tapering inwardly toward said hot end at an angle of from 0.5 to 10 and having a top wall and a bottom wall in loose fitting engagement with the tapered surface of said condenser, the hot end of said wedge extending into said retort, and a transverse circular baffle plate mounted on the cool end of said wedge having its circumferential edge in loose fitting relation with the wall of said condenser intermediate the hot and cool ends thereof.

6. Apparatus as defined in claim 5 in which said baffie plate has a centrally disposed aperture therein and at least one lug at the circumference of the hot face thereof.

7. Apparatus as defined in claim 5 in which the condenser and the wedge are tapered at an angle of about 3.

References Cited by the Examiner UNITED STATES PATENTS 8/1953 Burnett 26619 9/1965 Gibbs 26619 

1. APPARATUS FOR THE HIGH TEMPERATURE VACUUM REDUCTION AND CONDENSATION OF METAL WHICH COMPRISES A RETORT, A TUBULAR CONDENSER HAVING ONE END COMMUNICATING WITH SAID RETORT, SAID CONDENSER HAVING AN INTERIOR WALL SURFACE OF GRADUALLY DECREASING DIAMETER TOWARDS SAID ONE END, AND A METAL CROWN SUPPORTING DEVICE COMPRISING A WEDGESHAPED MEMBER HAVING A PAIR OF OPPOSED CONVERGING MAJOR SURFACES AND A PAIR OF OPPOSED CONVERGING MINOR SURFACES IN LOOSE FITTING ENGAGEMENT WITH SAID WALL SURFACE, SAID MEMBER HAVING A LONGITUDINAL AXIS ABOUT WHICH SAID SURFACES ARE SUBSTANTIALLY SYMMETRICALLY DISPOSED, SAID AXIS BEING SUBSTANTIALLY COINCIDENT WITH THE AXIS OF SAID CONDENSER WALL SURFACE, SAID SURFACES OF SAID MEMBER ALL CONVERGING TOWARDS ONE END THEREOF ADJACENT SAID ONE END 